Automatic telephone system



April 26 1927.

G. H. SIMMONS AUTOMATIC TELEPHONE SYSTEM @M0-@22am ADA 2 Sheets-Sheet 1 r Sau Q u I lll llllll u uuuu E uuuuuujuwujwuuumi f u A. i l

l ""Tu-umn E H- 51m-mans 1,626,103 April 26 1927' G. H. ssMMoNs v AUTOMATIC TELEPHONE SYSTEM original Filed Aug. 25, 1922 '2' sheetsfsheet 2 DDA TSE/:1r EH- Emmaus Patented Apr. 26, 1927.

UNITED STATES PATENT OFFICE.

GEORGE I-I. SIMMONS, 0F CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

AUTOMATIC ELECTRIC INC., OF CHICAGQ- ILLINOIS, A CORPORATION OF DELA- WARE.

AUTOMATIC TELEPHONE SYSTEM.

Application :tiled August 25, 1922, Serial No. 584,171. Renewed September 18, 1926.

The present invention relates in general to automatic telephone systems, but is more especially concerned with the trunking arrangements in such systems; and the object of the invention broadly stated is the design of a new and improved trunking system for an automatic telephone exchange or system, in which connections are established through the medium of serially related automatic switches, and in which one or more of the switches in series belonging to a major group of the system may be omitted for the sake of economy at the initial installation, without interfering with the use of a complete numbering system laid out in accordance with the ultimate capacity.

In order to carry out the general object of the invention as above set forth, what may be termed a discriminatingdigit absorber has been designed, which may be seized over two paths; when seized over one path one of the digits in the telephone numbers usually used to operate selectors o a group is eliminated, and when seized over the other path two digits in the telephone numbers usualy used .to operate selectors of a group are eliminated.

In View of the above it will he understood that the invention resides in the new trunkiug arrangement, and in the special means, the discriminating digit absorber, which is used to render this trunking arrangement practicable, and these features will now be described more fully, reference being` had to the accompanying drawings.

Referring to the drawings, Fig. l illustrates diagrammatically a trunlring system; while Fig. 2 shows an ordinary circuit diagram of a first selector together with the relay equipment above referred to as a discrimiuating digit absorber.

Referring to Fig. l, this diagram shows a portion ot a trunking system in an automatic telephone system having an ultimate capacity o' 1,000,000 lines, and using the well ltnown Strowger vertical and rotary switches operated according to the twowire system ot control. The system upon reaching its ultimate capacity will have a.

straight Strowger trunlring system, but upon original installation certain variations are made `tor the sake of economy. In

straight Strowger trunliing there are trunks extending from each oiiice to every other oiiice, and in a syste n or" the capacity described in this application the oiiice selection takes place in response to the second digit, there being more than ten and not over one hundred oftices in the system.

The operations which take placein a straight Strowger trunking system may be briefly described as follows: Referring to Fig. l, it will be assumed that a subscriber at substation A desires connection with a subscriber at substation A3. Upon removing his receiver the usual line switch C will operate to extend the calling line to an idle iirst selector, which it will be assumed is the selector E. The calling subscriber operates his calling device in accordance with the first digit of the called number which in this case is the digit O, causing the selector E to select an idle trunk eatending to an oiiice selector such as F, which in the particular illustration shown happens to have access to the oiiice in which A and A3 are located, it being, understood that the remaining levels may, and probably will have trunk connections extending to other oiiices.

The calling subscriber now operates his dial in accordance with the second digit of he called number, which as shown in the drawing is the digit 6, causing the selector F to select an idle trunk extending to the thousands selector such as G of the desired oifice.

The calling subscriber may now operate his dial in accordance with the remaining digits of the called number, which result in the operation of selectors such as G and II, and connector' I to extend the connection to the called line A3.

The above described trunking arrange ment will be recognized as the well known decimal or percentage trunking system which is in use in practically all automatic exchanges. Having briefly described the trunking layout usually used, the. features herein considered to be novel will now be pointed out.

In laying out a telephone system it is desirable to malte the division into offices at the start, and to locate the ofces in the various districts which cover the territory to be served in accordance with the best estimates ot future growth. It is not meant by this that all offices are n-ecessarily installed at once, ,tor some districts where a large future growth is probable may not be built up at all at the. time; or very sparsely; but what is meant is that an intelligent plan is devised based on a study of the probabilities. Those otlices are installed which are required for immediate needs, and others may be reserved for use in sections which may be built up in the future. lVhen such a plan is followed certain blocks ot' telephone numbers are. set aside for tuture use in each otlice and in each proposed omce in the system regardless ot the numbers ot subscribes originally served by that oiiice, and additions may be made tromtime to time without clninging the trunling plan originally adopted` or the telephone numbers originally assigned. The desirable teature that is to be retained at all events, it possible, is that ot so arranging the trunking at the startthat additions may be made from time to time without rearrangement oli the trunliing or changing ot telephone numbers.

Now it is quitev generally true that when an outlying oiiice is lirst installed it will serve at the start but a 'small traction ot its total ultimate capacity. For example some otlices may be installed to talre care ot a present total oin only lines, located iu a district which, althoiiigh marked 'lor a large ultimate growth, may nevertheless remain below the line ligure several years, while an adjoining district may contain oliices installed which take care of' a present 500 lines, but which like the 100 line otlices are marked tor an ultimate growth to 10,000 line offices. 1n the first instance it. will be evident that as long as the size ot the oltices do not exceed 100 lines, only the usual selectors required to select otlices, and counectors are required so tar as establishing` connections are concerned, and in the second instance as long as the size ol" the otlices do not exceed 1,000 liw es, only the usual selectors required to select the otiices and hundreds selectors and connectors are required; but since as stated it desired to assign uniform numbers at the start, in the first case'it i necessary to provide some sort ol an arrangement tor absorbing the two extra digits, and in the. second instance for absorbing one eXtra digit. Applicant has designed a discriminating digit absorber for accomplishing the desired results above set forth. This digit absorber may be placed in the switch series used in extending con-I nections to the 100 and 1000 line offices, and when a desired olilce' hasless than 100 lines, the digit absorber will be seized in a manner to cause two digits to be absorbed, however, it an oliice containing over 100 and less than 1000 lines is desired the digit absorber will be seized over another path and only one digit will be absorbed.

The arrangement can most clearly be r-X- plained by reference to Fig. 1 of the drawings. The selector E being vot the Strowger type has access to only-ten groups trunks and since the system contemplated .will Ahave more thanl ten oflices it is necessary to use second selectors to select oiiices; therefore :is will beseen the selector E 'has access thru the medium of a second selector such as F, or F', etc, to any of 100 otlices. lletween the selectors E and F the digit absorber DDA is inserted. rThis device is acce iible trom either the first or the third level et selector E and when taken for us via the lirst lev-cl it will absorb two digits, while ift taken lfor useby way ot the third level it will absorb only one digit.

In order to illustrate how the above arrangement works out the 100 line ollice to which the trunks such as 18 have access may be considered. As shown, the above otlice having connectors such as l2 will upon installation have been assigned a block of numbers from 180,000 to 189,999, but since only 100 lin-cs are provided tor, two digits, the second and third, must be absorbed or cancelled, and the block ot 100 numbers assigned to the 100 lines in use must be such that the 'fourth digit may operatel either the ottico selector F', a thousands selector (when the capacity is enlarged to 1000 lines), or a hundreds selector V(when the capacity is enlarged to the ultimate), without requiring any change in rthe trunking other than the installation of the additional 'selectors when needed. 1t will readily be appreciated that this result can be accoi'nplished by initiallv assigning a block ot k100 numbers in wh the second, third,'and fourth digits are the same, and the numbers assigned, theretore, run from 188,800 to 188,899. Now when the above 100 line otlicc is changer to u 1000 line eiiice the path extending 'troni the lirst level ot the selector E will be cornici/ted to the. upper path ot' the digit abf-gorber DDA, so, that thereafterv onlr the second digit willbe absorber, and the third digit will now operate the switch 1*" to the 8th level to trunks such 18. These tur-,nis will now extend to hundreds selectors, which will have access to the connectors 12 thru. the 8th evel.V lt will be readily seen that after the enlargement ot the above ofiq e has been'brought about Athe numbers u= il will be from 188,000 to 188,999. lt Lhe same olrice is increased'to serve 10,000 ln the digit absorber is entirely by-pathed. ie selector F- will respond to thel second digit. and the thousands selectors will be operated directly over trunks 18, while the hundreds selectors will be seized from the 8th level ot the thousands selectors.

linstance the station A',

A general description. having been given, a detailed description will now he gone into so that the real invention may be more clearly brought out.v For this purpose, it will first be assumed that a subscriber at substation A, Fig. 1, desires connection with a subscriber located in a 1,000 line o-tiicf-e, ter whose number is 311,851, the otlice at present serving lines No. 311,000 to 311,999.

The subscriber Vat A upon removing his receiver causes the line switch C to automatically extend the calling line to the selector' E 2) whereupon the line relay 50 will be energized and will close the circuit ot the slow acting release relay 51. Upon energizing, the latter relay prepares the circuits of the selector i'or operation in its vertical movement in the usual manner, and also completes a holding circuit which extends back to the line switch C of the calling line, and makes the calling line busy to other subscribers in the usual manner.

The calling subscriber may now operate his calling device in accordance with the iirst digit of the desired number, which is the digit 3, which determines that the called line is in a 1,000 line oiiice. Three interruptions are produced in the circuit of line relay 50, and the said relay is accordingly three times deenergized momentarily, transmitting at each deenergization an impulse of current through the slow acting series relay 52 and` the vertical magnet 56 to battery. By the operation of the vertical magnet, the selector shaft is raised three steps, whereupon the wipers 70-7 2, inclusive, and 42 will be standing opposite the level of the bank contacts in which are terminated the upper branch conductors leading to the digit absorber DDA. The slow acting relay 52 is energized in series with the vertical magnet, retaining the armature attracted throughout the vertical movement of the switch, and upon the closure of the vertical oi' normal springs 59 completes a circuit for the stepping relay 53. Upon energizing, relay 53 prepares a circuit for the rotary magnet 54 at its lower armature, and at its upper armature establishes a locking circuit for itself. At the end of the vertical movement of the switch, the slow acting relay 52 is deenergized and closes the circuit of the rotary magnet, which is thereupon energized to advance the wipers 70-72, inclusive, and 42 into engagement with the first set of bank contacts in the level opposite which they were raised. The rotary magnet 54 also breaks the locking circuit ot the stepping relay 53, which accordingly deenergizes and breaks the circuit of the rotary magnet, which thereupon deenergizes also and again closes its interrupter contact.

The operation now 4depends upon whether the trunk line with which the wipers have connected is busy or is not busy. If this trunk line is busy, the test contact associated therewith will be grounded and the stepping relay 53 will be energized over a circuit which extends by way ot the test wiper 71, armature 61 and its resting contact, otl' normal springs 59, interrupter contact of the rotary magnet, and the winding of the stepping relay 53 to battery. The stepping relay will, therefore, again close the circuit ot the rotary magnet 54, which will operate to rotate the switch wipers into engagement with the next set of bank contacts. This operation in which the stepping relay and the rotary magnet are alternately energized and -deenergized will continue as long as the test wiper 71 continues to engage grounded or busy test contacts. In the present case it will be assumed that the trunk shown in the drawing is the first idle trunk line, and when, therefore, the test wiper 71 arrives at test Contact 74 and the rotary magnet is deenergized, the stepping relay 53 will not again be operated, but instead the switching relay 55, which heretofore has been short circuited, will be energized by current flowing over the following circuit: Grounded conductor 64, winding of the switching relay 55, off normal springs 59, interrupter contact of the rotary magnet 54, and the winding ot the stepping relay 53 to battery. Owing tothe high resistance of the switching relay 55, stepping relay 53 is not operated. Upon energizing, relay 55 disconnects the incoming line conductors from the windings of the line relay 50 and extends them by way of karmatures and 62 and their working contacts, wipers and 72, bank contacts 73 and 75, conductors 77 and 80, and normally closed contacts of the switching relay 81 to the upper and lower windings of the line relay 82 of the digit absorber DDA, and at armature 41 and its working contact extends ground over wiper 42, bank contact 76, conductor 79, resting contact of armature 93 and the said armature, springs controlled by armature 89, andthe winding of relay 84 to battery.

Responsive to the closure of the alcove` described circuits, the relays 82 and 84 operate. The operation of relay 82 completes a circuit 'for slow release relay 83. The relay 83 (meratcs and at its upper armature and working contact places ground on the conductor 78 extending back to the switching relay and conductor G4, which was heretotore maintained grounded by the slow release relay 51 of the selector E, and at its lower armature and working contact clos-es one point in the circuit of relay 86. The relay 84 in operating, disconnects itself from ground at its armature 93, and completes a new holding circuit for itself at armature 89 and its working contact, the conductor 78 being grounded at this time by release relay 51 and a moment later by the slow release relay 83. Relay 84 also closes at its armature and its working contact a circuit for slow release relay 87, which relay also energizes.I Relay 87 in operating, at its armature 99 opens a point in the circuit of the switching relay 81, at its armature 104 and its working contact closes a point in the circuit of relay 86, and at its armature 103 and its working contact prepares a new circuit for itselt.

All the above described operations have taken place responsive to the seizure of the digit absorber, which is now in readiness to absorb the superfluous digit. The calling subscriber, upon operating the calling device to transmit the superfluous digit, causes the line relay 82 to be deenergized a plurality of times. Upon the first deenergization, a circuit is completed from grounded armature 88 and its resting contact, lower working contact of relay 83 and its associated armature, conductor 105, armature 10% and its working contact, springs controlled by armature 101, and the winding of relay 86 to battery. The relay 86 operates and at its armature 101 locks itselt1 up over the release trunk 78, at its armature 97 and its working contact closes a point in the operating circuit ot the switching relay 81, and at armature 102 and its working contact closes a point in a new holding circuit for slow relay 87, which relay has its original operating circuit now opened at armature 98. 1t will be noted that as long as the line relay 82 continues to vibrate, impulses will be transmitted 'from the grounded armature 88 and its resting contact, lower working contact and. armature of relay 88, conductor 105, working contact of armature 102 and the said armature, working contact ot armature 103 and the said armature, and the winding ot' relay 87 to battery, maintaining the latter relay energized. As soo-n as the impulses cease, relay 87 will deenergizc. The deenergization ot relay 87 causes a circuit to be closed for the switchingr relay 81 which may be traced as follows: Grounded conductor 78. resting contact of armature 99 and the said arn'iature, work', contact of a nature 87 a the said armature, resting Contact of armature and the said armature, \'vinding ot relay 81 to battery. The operation ot' the switching relay 81 disconnects its armatures 109 and 110 from the line relay and extendsthem to the conductors 108 and 108, which latter conductors terminate in the line relay oit a selectorl such as the selector F (Fig. 1).

The calling subscriber may now manipulate his calling device, causing the switch F to operate in the usual manner to seize a trunk line extending through the repeater R to the 1,000 line oil-ice in which A is located, after which the switches such as H and 13 may be controlled in well-known manner to compl-ete the connection.

It will now be assumed that a connection is set up to a line otlice. ln this case the calling subscriber will cause the .se-lector switch E to posit-ion its wipers 70-72, and Ll2 on an idle set ot' bank contacts such as 73-76, inclusive. Upon .seizing the digit absorber DDA over the latter branch, it will be noted that a circuit for the line relay 82 is completed in the previously described manner, but the relay 84 is not energized when the digit absorber is seized, there being no conductor extending from the bank contact 7 6. The relay 82, upon energizing, closes a circuit for the release relay 83 as beiore, and at the same time closes a circ-uit ttor slow release relay 85. rllhe relay 85 in operating, prepares a point in a new holding circuit for itseli:l at armature 94 and its working contact, at its armature 96 opens a point in the circuit of relay 87, and at armature opens a point in the circuit of the switching relay 81. All the above described operations take place upon seizure of the digit absorber, which is now in readiness to absorb the two superfluous digits in the called n u mber.

rilhe calling subscriber now operates his calling device in accordance with the first superfluous digit, causing the linerelay 82 to be deenergized a plurality of times as before. it the first deenergization ofline -relay 82, al circuit is completed from grounded armature 88 and its resting contact. lower working Contact and armature ot relay 83, springs controlled by armature 89, and the winding ot relay 84 to battery. The relay 84 energizes and locks itself to the conductor 78 in an obvious manner. At armature 91 the original energizing circuit -ot relay 85 is broken, at armature 90`one point in the circuit of relay 87 is closed, and at armature 92 a new circuit is closed for the relay 85. rlhis circuit may be traced from the grounded armature 88 and its resting contact, lower working contact. and armature or relay 88, armature 92 and itsrworking contact, arn'iaturete. andits working contact, and the winding of relay` 85 `to battery. rllhe relay 85 being slow to Yrelease will be now maintained energized. over the above traced circuit as long as the armature 88 of the line relay 82 vibrates. At the end of the series relay 82 remains energized causing the relay 85 to retract its armatures. Ars soon as the armature 96 restores a circuit for relay 87 is completed, from grounded conductor 78, working contact ot' armature 90 and the said armature, armature 96 and its resting Contact, resting contact of armature 98 and the said armature, and the winding of relay 87 to battery. f It will be noted that the digit absorber after absorbing one or' two superfluous digits, now has its circuits prepared in the same manner as that described for absorbing one digit.

The subscriber after dialling the second superfluous digit, will now be connected with the selector F', which he may control to ei;- tend the connection to either of the 100 line ofiices associated with trunks 12 or 18, in well-known manner.

It will be seen that I have devised a very desirable circuit arrangement 'for handling the digit or digits not required upon initial installation, which arrangement is suiiiciently flexible to permit the capacity of various offices of the system to be increased to a maximum without changing the general trunking layout, and without disturbing the original numbering scheme.

What I claim is:

l. In a telephone system, a plurality of oiiices, a calling lin-e in one of said ofiices, called lines in all of the offices, trunk lines extending between the office of the calling line and the other offices, means including series of automatic switches adapted to be operated by impulse series transmitted by a calling subscriber 'or extending conn-ectionsto said called lines, the switch series being of diiierent lengths in different office connections, While the impulse series transmitted by the calling subscriber in each connection is of the same length, and a digit absorber included in certain connections for absorbing one digit when lines in a certain office are called and for absorbing a greater number of digits when lines in other of said oces are called.

2. In a telephone system, a plurality of interconnected offices or exchanges, Ieach oice having series of automatic switches for completing connections, the number of switches used being dependent upon the connection established, a calling line, called lines having uniform digit call numbers, certain series of said switches responsive to a predetermined number of impulse series for completing a connection to a called line in one oftice, certain of said series of switches responsive to a lesser number'of impulse series for completing aV connection to a called line in another of said ofiices, and a digit absorber included in the latter connection for absorbing the superfiuous impulse series, certain of said series of switches responsive to a still smaller number of impulse series for completing a connect-ion to a line of a third oiiice, said digit absorber also included in the third connection for absorbing the two superfluous digits not required.

3. In a telephone system, a trunk line having two branches at the incoming end thereof, a digit absorber in said trunk at the junction of said branches, means for seizing said trunk via either of said branches and for transmitting series of impulses over the trunk, and means in said digit absorber for absorbing a varying number of series olE impulses depending on the branch in use.

4. In a telephone system, a trunk line having two branches atthe incoming end thereof, a digit absorber in said trunk at the junction of said branches, means for seizing said trunk via either of said branches and for transmitting series of impulses over the trunk, and means in said digit absorber for always absorbing one series of impulses, and additional means in said digit absorber for absorbing another series in case the trunk is seized by way of a particular one ot' said branches.

In a telephone system, a digit absorber, two paths over which said digit absorber may be taken for use, and discriminating means for causing said digit absorber to absorb a varying number ot digits depending on the path in use.

6. In a digit absorber, a switching relay, a line relay, a locking relay initially energized by said line relay responsive to the first impulse of a series, a circuit for said switching relay prepared by said locking relay, and a slow acting relay controlled by said line relay to hold said circuit open until the series of impulses is completed.

7. Inv a digit absorber, a slow acting relay, a line relay, a locking relay initially energized by said Yline relay responsive to the rst impulse of a series, a circuit for said slow acting relay prepared by said locking relay, a second slow acting relay controlled by said line relay to hold said circuit open until the first series of impulses is completed, a switching relay, a second locking relay initially .energized by said line relay responsive to the first impulse of a second series, a circuit for said switching relay prepared by said second locking relay, and means whereby said first slow acting relay is controlled by said line relay to hold the circuit of said switching relay open until the second series of impulses is completed.

8. In a telephone system wherein connections between lines are made by means of automatic switches responsive to a number of groups of impulses, a non-numerical switching device associated with the talking conductors for absorbing a variable number of groups of impulses, and means for disassociating said device from the talking conductors after it has absorbed the groups of impulses.

9. In a telephone system wherein connections between lines are made by numerical switches controlled by groups of impulses impressed upon the talking conductors ot' the line, a non-numerical switching device associated with thel talking conductors arranged to cause one of the groups of impulses tobe ineffective for actuating a numerical switch, and means operated responsire to the cessation of that group of impulses to disassociate the device from the talking conductors, said means including a locking relay Which is operated upon the commencement of said one of the. groups of impulses.

V10. In a telephone system wherein connections ybetween lines are made by numerical switches controlled by groups o impulses impressed upon the talking conductors oi' a line, a device associated with the talking conductors for causing one of the groups of impulses to beineifective for actuating a numerical switch, and means operated responsive to the cessation of that group of impulses to di'sassociate the device from the talking conductors, said means including a relay which is operated upon the commenceinentot Vsaid one ot' the groups of impulses and is maintained operated independent of the continuation oi' the impulses.

1l. The method ot establishing connections 'betwee'n one telephone line and a desired one oifa number of other lines, Which consists in sending a fixed number of groups of 'impulses over said iirst line and in extending the line with certain groups of impluses, said extensions being in` accordance with the number of impulses in some of the groups, and independent oi' the number of impulses in one of the groups, said one group being any one of a plurality of said fixed number of groups of impulses.

12. In a telephone system, the ymethod 'of extending a connection from one line to another line which consists in dialing the number of the desired line, and in extending the calling line toward the called line upon the dialing of each digit of the number except one, certain oi the extensions'being made in accordance and with the value of thedigit dialed and others being made independent otx the value of the digit.

13. In a telephone system, a trunk having two sections disconnected from each other, means for impressing a number of groups ot' impulses over one ot' said sections, means associated with said last named section for connecting the two lsections upon the cessation of the impulses of a certain group ot' said impulses, said `means being operated independent 'of the number ot iinpulses in said group, and variable means for determining which grup of impulses shall be the said certain group.

lei. In a telephone system, a Vdigit absorber, means tor extending different classes ot calls to the absorber, and means in the digit absorber for absorbing a'varying number oi digits depending upon the class ot call being extended.

In Witness whereof, I hereunto'subsc-ribe my name this 21st day of August, A. Di,

GEORGE H. SIMMONS. 

